Bone fixation system

ABSTRACT

The invention provides embodiments of a bone fixation system having a bone plate and a specialized screws system. The bone plate includes one or more bi-directional combination holes that can accommodate two bone screws in the same hole, the screws being oriented in non-parallel direction. In accommodating two screws in the same hole, one of the screws has a by-pass head.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Application No. 61/035,138, filed on Mar. 10, 2008, thecomplete disclosure of which is incorporated herein by reference in itsentirety.

FIELD OF THE INVENTION

The present invention relates to a system and method for bone fracturefixation.

INTRODUCTION

Conventional bone fracture fixation plate and screw systems work bydrawing the fracture fragments to the plate, and if designed with“compression” holes, the fracture fragments can be made to compressagainst each other to promote primary bone healing. However, the angularrelationship between the plate and screws is not fixed and can changepostoperatively. As such, this can lead to misalignment and poorclinical results.

One method of securing the screw to a bone plate involves the use ofso-called “locking screws.” A locking screw has a male thread on anouter surface of its head that interfaces with a female thread on theplate to lock the screw to the plate. Bone plates having threaded holesfor accommodating locking screws are known. For example, German PatentApplication No. 43 43 117 discloses a bone plate with threaded holes forlocking screws. As the relationship between the locking screws and theplate is fixed, locking screws provide a high resistance to shear ortorsion forces. However, locking screws have a limited capability tocompress bone fragments.

Another approach to construction of a bone plate involves use of“combination holes.” Combination holes in the bone plates have a domainfor non-locking screws and another domain for locking screws. Thelocking screws can only be applied in a direction perpendicular to theplate. (See, e.g., U.S. Pat. Nos. 6,669,701 and 7,354,441 to Frigg)However, only a one locking or a non-locking screw can be applied ineach of these “combination” holes along the bone plates.

Another bone plate hole configuration involves a “figure-eight” hole.(See, e.g., Universal Locking System available from Zimmer Holdings,Inc. (Warsaw, Ind.); see, also J. Bone and Joint Surgery, 89(7) 2007.)The figure-eight hole in the a bone plate has two parallel threadeddomains. A locking screw can be mated to one domain of the holes or tothe other domain of the same hole. In either case, the locking screw canbe applied only perpendicular to the bone plate. Further, only one screwcan be applied in each of these “figure-eight” holes along the plate.

In yet another approach, the bone plate has individual locking holes formating individual locking screws. (See, e.g., MIS Technique availablefrom Zimmer Holdings, Inc. (Warsaw, Ind.)) The individual holes areoriented alternating in one direction and in another direction (in theplane transverse to the longitudinal axis of the plate) away from theperpendicular to the plate. However, for such a configuration, half ofthe screw holes may not be suitable for use. In the worse case scenario,none of the holes can be used.

BRIEF DESCRIPTION

A system and method for bone fracture fixation, especially long bonefracture fixation, in acute injury or reconstruction setting isprovided. The system includes a bone plate and a specialized screwsystem. The bone plate has an upper surface and an opposed lowersurface, which contacts the bone to be fixated. The bone plate includesat least one, and suitably a plurality of bi-directional divergentcombination holes, spaced apart along its length. Each bi-directionalcombination hole has two screw domains. The central axis of the domainsare at angles to each other and in reference to the lower plate surface,i.e., the directions of the screws positioned in each domain of acombination hole are non-parallel. The specialized screw system includesa by-pass head screw having a cut away such that “by-pass” head of thescrew allows placement of a “full head” screw immediately adjacent inthe same combination hole. The screws may have a threaded portion alongtheir shafts or may be non-threaded pegs. The specialized screws may belocking (i.e., threaded head) or non-locking.

In some embodiments, the invention provides a bone plate which has asuitably serpentine shape to optimize the use of materials around thebi-directional holes. The bi-directional holes may be disposed adjacentbut offset or angled to one another, e.g., along the length of a boneplate. In other embodiments, the invention provides a bone plate, whichhas a suitably linear shape. The combination holes may also be placedadjacent to one another but are offset or angled with respect to eachother and with respect to the longitudinal axis of the plate. Thecentral axis of the domains of the combination holes are configured atan angle with respect to each other and with respect to the lower platesurface. The bone plate may include both combination and non-combinationholes.

In another aspect, a method of fixating bone factures is provided whichincludes positioning a bone plate having a plurality of bi-directionaldivergent holes therethrough to a fracture site, and inserting bonescrews through the bi-directional holes of the bone plate into a bone orbone fragments to fixate the fracture, the screws being oriented in thebone in non-parallel directions. A by-pass head screw allowsaccommodation of a full head screw in the same hole.

Other advantages and a better appreciation of the specific adaptations,variations, and physical attributes of the invention will be gained uponan examination of the following detailed description of the invention,taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be better understood and appreciated by reference tothe detailed description of specific embodiments presented herein inconjunction with the accompanying drawings of which:

FIG. 1 is a top plan view of a serpentine plate configuration of a boneplate with a plurality of bi-directional screw holes, all in accordancewith embodiments of the invention;

FIG. 2 is a top plan view of a linear plate configuration of a boneplate with a plurality of bi-directional screw holes, all in accordancewith embodiments of the invention;

FIG. 3 depicts perspective views of the serpentine and linear bone plateconfigurations, illustrating both combination bi-directional holes andconventional holes;

FIG. 4 is a top view of serpentine plate configuration and across-sectional view, along plane A-A′, of the bi-directional divergentholes, illustrating the angled axes of the domains of each combinationhole;

FIG. 5 is a perspective view of the directionality of individual screwswhen installed in bi-directional divergent holes;

FIG. 6 is a perspective view of a by-pass locking screw in accordancewith embodiments of the invention; and

FIG. 7 is a top, cutaway view of a standard locking screw and a by-passhead screw, both positioned in the same bi-directional hole inaccordance with embodiments of the invention.

FIG. 8 depicts perspective views of the serpentine and linear bone plateconfigurations, having only combination bi-directional holes.

DETAILED DESCRIPTION

A bone fixation system embodying the principles illustrated inembodiments of the invention is provided. The system includes a boneplate and a specialized screw system.

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of the structure and function set forth in the followingdescription or illustrated in the appended drawings. The invention iscapable of other embodiments and of being practiced or of being carriedout in various ways.

Also, it is to be understood that the phraseology and terminology usedherein is for the purpose of description and should not be regarded aslimiting. The use of “comprising,” “including,” or “having” andvariations thereof herein is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.“Comprising” also encompasses the terms “consisting of” and “consistingessentially of” The use of “consisting essentially of” means, e.g., thata device may include additional features, but only if the additionalfeatures do not materially alter the basic and novel characteristics ofthe device.

Unless specified or limited otherwise, the terms “mounted,” “connected,”“supported,” and “coupled” and variations thereof are used broadly andencompass both direct and indirect mountings, connections, supports, andcouplings. Further, “connected” and “coupled” are not restricted tophysical or mechanical connections or couplings.

Further, no admission is made that any reference, including any patentor patent document, citied in this specification constitutes prior art.In particular, it will be understood that unless otherwise stated,reference to any document herein does not constitute an admission thatany of these documents forms part of the common general knowledge in theart in the United States or in any other country. Any discussion of thereferences states what their authors assert, and applicant reserves theright to challenge the accuracy and pertinence of any of the documentscited herein.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Unless otherwise noted, technical terms are used according toconventional usage. However, as used herein, the following definitionsmay be useful in aiding the skilled practitioner in understanding theinvention. Such definitions shall be applied, unless a differentdefinition is given in the claims or elsewhere in this specification.

The term “bone screw”, as used herein, refers to a screw configured tobe inserted into bone. The screw may be threaded, or have a threadedportion, along its shaft, or may be non-threaded shaft, e.g., anon-threaded or smooth peg. The bone screw may also be a locking screwwith threads on the outer surface of its head. The head of the screw maytake several shapes from hemispherical to hexagonal recessed.

As used herein, the term “combination hole” or “combination aperture” ismeant to refer a hole or aperture in a bone plate that is dimensionedand configured to have two portions or domains, each of which canaccommodate a screw such that two screws can be positioned in the samecombination hole.

As used herein, the term “bi-directional” or “bi-angular” in referenceto a combination hole or aperture is meant to refer to a hole oraperture in a bone plate that is dimensioned and configured toaccommodate two screws wherein, when the screws are positioned in thesame hole, the screws are directed at angles to each other and to thebone plate, i.e., the directions of the two screws in the samecombination hole are non-parallel.

The term “by-pass head” refers to a specialized screw in accordance withembodiments of the invention in which the head of the screw has asubstantially circular or spherical segment, i.e., the head is cut by achord or plane. The by-pass head screw may be locking or non-locking.

In view of the aforementioned disadvantages inherent in conventionalbone fixation systems, a novel system and method for fixating bonefractures, especially long bone fractures, is provided. Given that manyfractures have not only transverse fracture components but also obliqueor, even rather frequently, long fracture lines along the bone, theinventor has been found that screw placement, in case of fracturefixation with a plate, directed away from a plane perpendicular to thebottom surface of the plate is advantageous. In one aspect, a bi-angularor bidirectional combination screw hole configuration in a bone plate isprovided which is in the form of at least one, and suitably a pluralityof, such combination holes or apertures, each hole of which has twodomains for holding and positioning screws. One domain of the hole maybe suitably used to mate a conventional bone screw, e.g., a non-lockingscrew, in one direction away from the perpendicular or even along theperpendicular to the bottom surface of the plate, while the other domainof the same combination hole is suitably used to mate a screw, e.g., alocking screw, in an entirely different non-parallel direction. In use,two screws may be suitably mated in each bi-angular hole wherein onescrew is a conventional bone screw and the other is a by-pass head screwin accordance with embodiments of the invention. The direction of thescrew placement per hole depends on the optimal configuration forindividual fracture fixation and is not limited as in the existing priorart devices. It is also understood that the combination hole mayaccommodate two by-pass head screws as well.

Reference is now made to FIGS. 1-8 in which a bone fixation system,generally designated by reference numeral 10, in accordance with oneembodiment of the invention is shown. System 10 includes a bone plate 20and a screw system 21 for stabilizing bone segments. In one embodiment,bone plate 20 is defined by a first surface 22 and a secondbone-contacting surface 24 that is opposed to the first surface 22. Boneplate 20 is suitably elongate, with a length 23 and a longitudinal axis25. Bone plate 20 can optionally be curved along its length, enablingbone plate 20 to be anatomically contoured, i.e., to contour a bonesurface.

In an illustrated embodiment, bone plate 20 includes a plurality ofcombination screw apertures or holes 26 which extend through the firstand second surfaces 22, 24 of bone plate 20. Each of the combinationapertures or holes 26 has a predefined shape and size. Each of theapertures or holes 26 is suitably shaped as a bi-angular or an offsetfigure-eight, and is dimensioned and configured to receive a pair ofscrews 32 and 34 therethrough. Screws 32, 34 are used to anchor boneplate 20 to the particular bone segments that require fixation, i.e.,are suitable for insertion into bone. Each hole 26 has two domains 28and 30, respectively, which are substantially circular but overlapping,forming an offset figure-eight overall shape. Each domain is dimensionedand configured to receive one of the pair of screws therethrough.Domains 28 and 30 may or may not be provided with internal threads 41.Internal threads 41 may engage the threads of a threaded head bonescrew.

Certain variations of the invention are set forth and illustrated in thefigures. As shown in FIG. 4, one domain of a combination hole has a holeaxis 36 and the other a hole axis is 38. The axes are angled withrespect to each other, i.e., the axes are non-parallel. As shown in FIG.7, screws 32, 34 have a head portion 36 and 38, respectively, at aproximal end 42. Each screw 32, 34 has an elongate body or shaft 44 thatmay include a threaded portion 46, as shown in FIG. 5, and/or a threadedhead portion 45. Such external threads 45 disposed along the screw headcan mately engage internal threads 41 of the domains of thebi-directional hole 26. It is understood that non-threaded screws orpegs as well as conventional threaded head screws can also beaccommodated in bidirectional holes 26 as shown in FIG. 5.

Bone plate 20 may have many shapes. In one variation, as shown in FIG.1, bone plate 20 may have a suitably serpentine shape 52 with, e.g., anarched cross section contouring the bone surface. As described, theserpentine shape coupled with the angled combination holes permit amaterials-conserving plate configuration. However, the plate can beconfigured in many different shapes and sizes to accommodate anysituation. For example, FIG. 2 illustrates another variation of theinvention as a linear plate configuration 54, and FIGS. 3 and 8 showperspective views of both the serpentine plate 52 and linear plate 54.The embodiments of FIG. 3 illustrate bone plate 20 with both combinationbi-directional holes and conventional holes. The embodiments of FIG. 8illustrates bone plate 20 having only combination bi-directional holes.

As described herein, in one variation, the underside of the bone platemay be concave, thus allowing the plate to conform to the roundedsurface of the tibia, femur, humerus, forearm bone, and other bones withwhich embodiments of the invention may be used. The concaveconfiguration of the underside also allows a conventional bone screw tobe inserted obliquely through the plate hole when a small bone fragmentmust be gripped and pulled against the plate.

To accommodate two screws in a single combination hole, a conventionalhead, (e.g., substantially circular or hemispherical), bone screw 32 maybe placed in at least one of the domains 28, 30 of holes 26 and providecompression of the fractured bone fragments. In the other domain, screw34 has a by-pass head 50. By-pass head 50 of screw 34 allows two screwsto be accommodated in the same single combination hole.

For example, a by-pass head screw may be placed eccentrically withrespect to the hole, as is necessary for attaining compression of afracture. With the by-pass head screw in place in the first domain ofhole 26, the second domain of hole 26 may then receive the conventionalfull-head screw 32, as such variation is shown in FIG. 7. As describedhereinabove, the second domain of the hole provides an increasedangulation of the bone screw with respect to the bone plate and theother screw. That two divergent screws are mated to the same bi-angularhole provides additional fixation to bone because screws, orienteddivergently into the bone, offer significantly more resistance to pullout than any existing configuration. Torsional resistance is alsotheoretically greatly increased. FIGS. 4-7 further illustrateembodiments of the invention with respect to the bi-directional screwholes and specialized by-pass screw head.

As noted, one of the two screws mated into the bi-angular hole can be aconventional nonlocking screw which is capable of bringing the bone tothe plate. The other screw can then be mated to the plate and bone in alocking fashion. In current prior art devices, a surgeon has tosacrifice several holes to bring the bone to the plate and then use theremaining holes in a “locking mode”. In accordance with the invention,no hole is “wasted” and every hole could offer enhanced fixation beyondwhat an existing locking or non-locking screw can.

Similarly, a non-locking by-pass head screw can be made to lock to theplate with a conventional locking screw that is mated to the adjacentdomain of the same bi-angular screw. The bi-angular screw hole matedwith two divergent screws provides added fixation in fractures adjacentto the softer bone proximate to joints, specifically, periarticularfractures and those that require articular subchondral support such asin distal radius fractures, tibial pilon fractures, tibial plateaufractures, etc.

Bone plate 20 may be provided with any number of holes 26 as may besuitable for a specific surgical application. Holes 26 may be disposedalong the length 23 of bone plate 20; variations are illustrated, asshown, e.g., in FIGS. 1 and 2. One of ordinary skill in the art willknow and appreciate that bone plate 20 may be provided with other typesand configurations of holes 40, e.g., non-combination screw holes, inaddition to combination holes 26, as illustrated. For example, inaddition to one or a plurality of bi-directional combination screws,bone plate 20 may be provided with substantially cylindrical holes,threaded holes, or any other type of hole known to one of ordinary skillin the art.

To facilitate insertion, the threaded screws can be self-tapping screwsor pre-drilled with the aide of a drill guide. Additionally, the screwscan be cannulated for insertion of a guide wire to guide screwplacement. As noted, the screws may have a smooth shaft such as a peg.The hole domains may have a substantially conical shape with adoublelead thread. The length of the individual screw shaft and theshaft (threaded or smooth) configuration can be selected for theparticular application. For example, the individual screw shaft can alsobe smooth with a rounded, diamond, or trocar shaped tip. The domains mayalso be threaded or smooth, depending on whether the domain isaccommodating a threaded screw or a peg.

In practice, embodiments of the invention provide methods of fixatingbone fractures. The method includes positioning a bone plate having,along its length, a plurality of bi-directional divergent holestherethrough to a fracture site, inserting bone screws through thebi-directional holes of the bone plate into a bone or bone fragments tofixate the fracture, the screws being oriented in the bone innon-parallel directions.

It should also be noted that during the surgical act of applying theplate to the fractured bone, critical vessels or nerves or muscle orother soft tissue may be in the way of the path of the intended drillhole. In accordance with embodiments of the invention, a surgeon is ableto avoid undue retraction on the soft tissue or even minimize softtissue dissection by choosing the more suitable direction afforded bythe bi-directional hole design. Therefore, an additional benefit of thebi-directional design is its versatility, minimizing the requirement forsoft tissue dissection and retraction.

In summary, the full mechanical advantage of the combination holeconfiguration in accordance with embodiments of the invention isrealized when two screws are mated to the same bi-directional orbi-angular hole. The head of one screw to be mated to the plate suitablyhas a by-pass head to allow the placement in the same hole of a secondscrew with a conventional full-headed screw. Having two fixed-anglescrews oriented in divergent directions into the substance of the boneenhances the pull out strength of the plate from the bone far beyondthat of a single locking screw oriented perpendicular to the plate.

The foregoing description is considered as illustrative only of theprinciples manifest in embodiments of the invention. Further, sincenumerous modifications and changes may readily occur to those skilled inthe art, it is not desired to limit the invention to the exactconstruction and operation shown and described, and accordingly, allsuitable modifications and equivalents are considered to fall within thescope of the invention. Various features and advantages of the inventionare set forth in the following claims.

All publications, patents and patent applications referenced in thisspecification are indicative of the level of ordinary skill in the artto which this invention pertains. All publications, patents and patentapplications are herein expressly incorporated by reference to the sameextent as if each individual publication or patent application wasspecifically and individually indicated by reference. In case ofconflict between the present disclosure and the incorporated patents,publications and references, the present disclosure should control.

1. A bone plate, comprising: an elongate member having an upper surface,lower surface and a longitudinal axis, and at least one bi-directionaldivergent combination hole therethrough from the upper surface to thelower surface, configured and dimensioned to receive a pair of bonescrews configured to be anchored into a bone or bone fragments.
 2. Thebone plate of claim 1, wherein, when the screws are positioned in thebi-directional hole, the bi-directional hole orients the screws innon-parallel directions.
 3. The bone plate of claim 2, wherein one ofthe pair of screws has a by-pass head configured to accommodate theother screw having a full head.
 4. The bone plate of claim 1, whereinthe member is in a serpentine shape.
 5. The bone plate of claim 1,wherein the member is linear in shape.
 6. The bone plate of claim 1,wherein the bi-directional combination hole comprises two domains, eachconfigured to accommodate a bone screw.
 7. The bone plate of claim 6,wherein the two domains are configured as an offset figure-eight.
 8. Thebone plate of claim 6, wherein at least one of the domains is threaded.9. The bone plate of claim 6, wherein at least one of the domains isnon-threaded.
 10. The bone plate of claim 6, wherein one of the screwsis a non-locking screw and the other is a locking screw.
 11. The boneplate of claim 6, wherein both screws are locking screws.
 12. The boneplate of claim 2, wherein one of the screws is non-threaded.
 13. Thebone plate of claim 2, wherein at least one of the bi-directional holesis configured to direct one of the pair of screws, when inserted,oblique to or perpendicular to the longitudinal axis of the member. 14.The bone plate of claim 6, wherein each domain has a hole axis, and thehole axis of one domain is non-parallel to the hole axis of the otherdomain.
 15. The bone plate of claim 1, further comprising a plurality ofbi-directional combination holes.
 16. The bone plate of claim 15,wherein the holes are configured to be offset with respect to each otheralong the longitudinal axis of the member.
 17. The bone plate of claim15, wherein the bi-directional holes alternate with conventional holes,the conventional holes configured to receive a bone screw.
 18. The boneplate of claim 1, wherein the bone plate is anatomically contoured. 19.The bone plate of claim 18, wherein the lower surface of the bone plateis concave.
 20. A bone screw capable of providing compression across afracture, comprising a by-pass head and an elongate shaft extending fromthe head to a distal end of the screw.
 21. The screw of claim 20,wherein the by-pass head further comprises a threaded portion about itsouter surface.
 22. The screw of claim 20, the by-pass head furthercomprises a non-threaded portion about its outer surface.
 23. The screwof claim 20, wherein, when the screw is configured to be positionedwithin a bi-directional hole of a bone plate, the by-pass headconfigured to accommodate the placement of a full head screw or pegwithin the same hole.
 24. A bone fixation system, comprising: a boneplate and a by-pass head bone screw; the bone plate having an uppersurface, a lower surface, a longitudinal axis, and at least onebi-directional combination hole extending through the upper surface andthe lower surface; the bi-directional combination hole having twodomains, each domain configured to accommodate a bone screw; the by-passhead screw configured to, when positioned in the bi-directional hole,permit a full head screw to be accommodated in the at least onebi-directional combination hole; each screw having an elongate shaft,and when each is positioned in the bi-directional combination hole,their shafts are oriented in non-parallel directions.
 25. The bonefixation system of claim 24, wherein the two domains are configured asan offset figure-eight.
 26. The bone fixation system of claim 24,wherein, when a screw is positioned in the bi-directional combinationhole, its shaft is oriented perpendicular or oblique to the longitudinalaxis of the bone plate.
 27. The bone fixation system of claim 24,wherein the bone plate further comprises a plurality of bi-directionalcombination holes, the holes being offset with respect to each otheralong the longitudinal axis of the plate.
 28. A method of fixating bonefractures, comprising positioning a bone plate having a plurality ofbi-directional divergent holes therethrough to fracture site, andinserting bone screws through the bi-directional holes of the bone plateinto a bone or bone fragments to fixate the fracture, the screws beingoriented in the bone in non-parallel directions with respect to eachother.
 29. The method of claim 28, wherein each bi-directional holeaccommodates a pair of screws, at least one of the pair of screws is aby-pass head screw.
 30. A kit, including: a bone plate having an uppersurface, a lower surface and a longitudinal axis and at least onebi-directional divergent combination hole therethrough from the uppersurface to the lower surface, which is configured and dimensioned toreceive a pair of bone screws configured to be anchored into a bone orbone fragments; and at least one by-pass head screw engageable in thebidirectional hole.
 31. A bone plate system, comprising: an elongatedplate member having a plurality of bi-directional combination holestherethrough, the holes configured as offset figure-eights; and one ormore bone screws engageable into the bidirectional holes wherein eachcombination hole is configured and dimensioned to orient two screwsinsertable therein in non-parallel directions, one of the screws being aby-pass head screw.